Conventionally, in the field of vehicles such as automobiles, there is known an insulated wire in which an insulator coats the outer circumference of a stranded wire conductor having a plurality of conductor element wires twisted together.
As the stranded wire conductor, specifically, Patent Document 1 discloses a stranded wire conductor including a stainless element wire and a plurality of bare copper element wires that are twisted together on the outer circumference of the stainless element wire. Further, the document describes a technology for softening copper in which the bare copper element wires is subjected to heat treatment so as to improve the elongation which was deteriorated by work-hardening after the bare copper element wires were twisted together and subjected to circular compression.